The present invention relates to an electrical machine, preferably a three-phase generator for motor vehicles. More particularly, the present invention relates to an electrical machine which has a surface-cooled stator with two stator windings inserted in slots of a stator plate stack.
It is already known from the Japanese Utility Model Publication 57-65570 to provide the stator housing of an electric motor with cooling fins for guiding off heat. These cooling ribs, together with the annular spaces at the winding ends of the stator winding, are filled with a heat conducting mold resin after the stator plate stack has already been inserted into the housing with the stator winding. In so doing, the winding ends are completely embedded in the mold resin so that the heat losses generated in them can be guided outward. A disadvantage of an electrical machine produced in this way consists in that the entire prefabricated stator, including its housing, must be inserted in a press or injection mold for embedding the winding ends in heat conducting plastic, which requires special steps for sealing the injection or press mold. Such a solution becomes even more costly when the electrical machine has two stator plate stacks with stator windings located one after the other in the axial direction and when these systems are inserted into a pot-shaped stator housing in addition.
Such a three-phase generator for motor vehicles having a double-generator system in a closed, water-cooled housing is known (FIG. 5) from DE-OS 31 28 081 (R. 6932, FIGS. 5 to 7). The winding ends of the two systems are exposed. Consequently, due to the relatively poor heat conduction at the winding ends, the output of such an electrical machine is limited and its outer diameter is relatively large. Moreover the two stator plate stacks are inserted into the cylindrical stator housing from both sides, which cannot be realized in a pot-shaped construction of the housing.